The present invention relates to foreign object detection (FOD) of a wireless power transfer system such as a wireless charging system, and more particularly, to a method for performing wireless charging control, and an associated apparatus.
FOD is a hot topic in the field of the wireless charging technologies since a foreign object may endanger the user of a wireless charging system. For example, a foreign object such as a Digital Versatile Disc (DVD) typically has a thin layer of metal. As the thin layer of metal may be easily heated during wireless charging due to the eddy currents, the DVD can be regarded as a dangerous foreign object. Therefore, when a foreign object is detected, it is better to stop wireless charging.
According to the related art, a conventional FOD method based on power loss detection is typically designed for an inductive wireless charging system, rather than a resonant wireless charging system. In a situation where the conventional FOD method is applied to the inductive wireless charging system, the conventional FOD method can be used for detecting a foreign object near the inductive wireless charging system. However, in a situation where the conventional FOD method is applied to the resonant wireless charging system, some problems may be encountered. For example, it may be observed that there is only a slight difference between the power loss in a first case in which a mobile phone is wirelessly charged in the landscape orientation and the power loss in a second case in which this mobile phone is wirelessly charged in the portrait orientation and a DVD having the size of 8 centimeters (cm) is positioned nearby, which means it is hard to distinguish one of the two cases (e.g. any of the cases A and B) from the other of the two cases. As a result, a false alarm (e.g. the first case is erroneously recognized as the second case) or detection failure (e.g. the second case is erroneously recognized as the first case) may occur.
For the user's safety, the aforementioned detection failure should be prevented. In addition, for the user's convenience, the aforementioned false alarm should be prevented. Thus, when one is trying to implementing a resonant wireless charging system such as that mentioned above according to the conventional FOD method, there is a tradeoff between reducing the probability of the aforementioned false alarm and reducing the probability of the aforementioned detection failure. Thus, a novel method is required to enhance the wireless charging control of a wireless charging system.